1. Field of the Invention
The present invention relates to a rotary electric shaver in which a cutter frame held by a shaver main body is provided with a plurality of cutter units, each of which includes an outer cutter and an inner cutter to be rotated while bringing the inner cutter into resilient contact with the outer cutter from below.
2. Description of the Related Art
In this type of electric shaver, when a substantially discoid outer cutter is pressed against skin with a high pressing force, the outer cutter tends to deeply dig into the skin, undesirably causing excessively deep shaving or an excessive pressure of contact between the outer rim of the outer cutter and the skin, possibly resulting in discomfort of the user of the shaver. As a solution thereto, it has conventionally been proposed to surround the outer periphery of the outer cutter by a cutter circumferential rim (skin supporting rim) so as to prevent the contact pressure between the outer cutter and skin from becoming excessive (refer to JP 09-503424(T).
In the rotary electric shaver disclosed in the aforesaid JP 09-503424(T) (corresponding to WO 96/02368, U.S. Pat. No. 5,625,950 and EP 0719203A), the cutter circumferential rim (skin supporting rim) is movably retained relative to a cutter frame, and the outer cutter is movably retained relative to the cutter circumferential rim. When the outer cutter is brought into firm contact with skin, the skin around the outer cutter depresses the cutter circumferential rim, so that the contact pressure is distributed between the outer cutter and the cutter circumferential rim, thus reducing the contact pressure applied to the outer cutter.
The aforesaid patent also discloses adjoining cutter circumferential rims connected with a hinge to prevent the heights of the adjoining cutter circumferential rims from becoming significantly uneven thereby to ensure that the shaving surface of a head unit smoothly slides along a curved skin surface.
The rotary electric shaver disclosed in the aforesaid JP 09-503424(T) poses a problem in that, since the outer cutter is movable relative to the cutter circumferential rim, increasing the travel amount (the amount of depression or the amount of rocking) of the outer cutter causes the edge of the outer cutter to be easily caught by the opening rim of an outer cutter mounting port of the cutter circumferential rim. More specifically, the outer cutter is inserted from below into the outer cutter mounting port of the cutter circumferential rim, and the flange of the outer cutter engages the inner edge of the outer cutter mounting port of the cutter circumferential rim. Therefore, firmly pressing the outer cutter against skin causes the outer cutter to deeply dig into the cutter circumferential rim.
Further, since adjoining cutter circumferential rims are connected with a hinge, a vertical movement, a rocking or a circular movement of one cutter circumferential rim causes an adjacent cutter circumferential rim to move up and down or rock, preventing each cutter circumferential rim from independently moving. In other words, when one outer cutter moves down or rocks along an uneven skin surface, the adjacent cutter circumferential rim and the outer cutter also moves down or rocks together, adversely affecting the performance of the adjacent outer cutter.
Further, more members interlock with the vertical movement or rocking movement of a single outer cutter, resulting in higher resistance applied to a vertical travel of the subject outer cutter. In addition, the presence of the hinged structure between cutter circumferential rims inevitably leads to a smaller outside diameter of the outer cutter or a smaller shaving area of the head unit, i.e., the total area of the shaving surfaces of the individual outer cutters. On the other hand, increasing the outside diameter of the outer cutter would increase the size of the cutter frame.